Discharge lamp and circuit



Feb. 18, 1941. D. s. Gus-HN Erm.

DISCHARGE LAMP AND CIRCUI-T Filed April 23, 1958 INVENTOR 6I 60S/7N l? F. HAD/.5' Jk- BY ug Maw-WN ATTORNEY Patented Feb. 18, 1941 UNITED STATES PATENT OFFICE DISCHARGE LAMP AND CIRCUIT Application April 23, 1938, Serial No. 203,757

11 Claims.

The present invention relates to discharge lamps and particularly to a starting arrangement therefor which prolongs the useful life of such lamps.

Discharge lamps at the present time are well known to the art, and one of the characteristics oi' lamps of this type is the difilculty in starting a discharge between the electrodes. In the majority of cases discharge lamps employ electrodes of the type known as cold" electrodes, that is to say, electrodes which are heated to the point of emitting electrons solely by the resulting discharge. This requires a comparatively high starting voltage, and since lamp lii'e is dependent more on the number of times the lamp is started, rather than on the number of hours burning, such lamps have had a comparatively short useful life.

To facilitate starting and thus to prolong useful life, it has been suggested in the art to employ "hot electrodes which are heated to an electronemitting temperature prior to the imposition o a voltage across the electrodes of the lamp. In instances of this kind, the heating elements for the electrodes are usually connected in series and some switching device is employed to intenrupt the flow of current through the heating elements after the initiation of a discharge, since the electrodes may then be heated by the discharge itself.

Despite the employment of heated electrodes to lower the starting voltage, it nevertheless has heretofore been higher than the customary domestic source of supply of 110 volts. Moreover, the switching device for interrupting the flow of current through the heating elements for the electrodes has been a power consuming device, which is objectionable from the standpoint that the average consumer pays for electrical energy which is not converted into visible light.

It is accordingly the primary object of the present invention to provide a starting arrangement for discharge devices which is operable from the customary domestic source of supply.

Another object of the present invention is the provision of a starting arrangement for gaseous discharge lamps having a low starting voltage, enabling them to be readily energized from the usual commercial source of supply.

Another object of the present invention is the provision of a starting arrangement for gaseous discharge lamps wherein starting of the device from the customary domestic source of supply is facilitated, and substantially all of the current derived from the source of supply is converted into visible light.

Another object of the present invention is the provision of an impedance device connected in series with a heater element for the electrodes which has a negative temperature coemcient so that upon the initiation of a discharge between the electrodes, current ow through such device is negligible.

Another object of the present invention is provision of a thermal relay for interrupting the the eliminating any loss of power.

Still further objects of the present invention will become obvious to those skilled in the art by reference to the accompanying drawing wherein:

Fig. 1 is a schematic diagram of a starting circuit for a gaseous discharge device in accordance with the present invention;

Fig. 2 is a. schematic diagram of a starting cuit for a gaseous discharge device showing still ciranother form which the present invention may take;

Fig. 3 is a side elevational view showing form which the relay shown in the circuit of one Fig.

2 may take in accordance with the present invention;

Fig. 4 is a sectional view taken on the IV-IV of Fig. 3 looking in the direction indicated by the arrows;

line

Fig. 5 is a side elevational view of still another another form which the relay, as shown in the circuit of Fig. 2, may take in accordance with the present invention, and

Fig. 6 is a sectional view taken on the VI-VI of Fig. 5 and looking in the direction indicated by the arrows.

Referring now to the drawing in detail, in

l a gaseous discharge device is shown comprisline Fig.

ing an evacuated envelope 5 provided with filamentary electrodes 8 and 1 consisting of a refractory metal, such as tungsten or the like,

and

which may be coated with a material which emits a copious iiow of electrons when heated, such as the oxides of barium, strontium, or the like.

The envelope is provided with an ionizable dium such as mercury, sodium, or other readily volatile material, as well as an inert gas, such as argon, neon, etc., to facilitate starting.

The

electrodes 6 and 'I are connected to a suitable source oi electrical energy i, such as the customary domestic source oi 110 volts, and a selfinductance 9 is connected in series with the electrodes and the source l.

These electrodes C and 1 are also connected in series through a resistance device Il and a capacitor I2 of approximately 6 microfarads with the capacitor I2 and self-inductance I being of such dimensions that they are in or near resonance for the fundamental frequency of the alternating current source. The resistance element Il has a negative temperature coeiiicient so that when cold, the resistance thereof is comparatively high; and, conversely, when hot, the resistance thereof is low. This device may cornprise a glass tube filled with silicon crystals or the device may be formed of a solid rod oi' zinc oxide or similar material, so long as it has a negative temperature coeilicient.

When the lamp 5 is connected to the 110 volt source 8, upon the closure of a suitable switch (not shown), the total reactance of the lamp circuit is low and the resistance is high, with the result that a small current initially flows. This current gradually heats the electrodes i and 1 to an electronemitting temperature and at the same time gradually heats the resistance element III. As the resistance element heats up, its resistance gradually decreases with a corresponding increase in current. The increase of current through the resistance device III is gradual enough that the increase of the electrode temperature does not lag appreciably.

By the time the current flow through the device I increases to substantially maximum, the voltage across the capacitor I2 rises to a value sumcient to strike an arc between the electrodes I and l. Upon the initiation of the discharge, the resistance element I0 and capacitor l2 are practically disconnected from the circuit, since the current will follow the path of. least resistance across the arc, and any current flowing through the resistance I0 and device I2 is very inappreciable.

inasmuch as the resistance device III practically disconnects the capacitor I2 due to its high `in crease in resistance, the possibility of surge current flowing through the lamp is substantially eliminated. Moreover, the voltage available for starting the arc is actually higher than the voltage across the condenser, which voltage is not dangerously high, reaching a maximum of only approximately 150 volts.

The various elements of the circuit Just described may be so adjusted that in case the lamp fails to start for any reason, the current will not be abnormally high, which thus dispenses with the necessity of other protective devices, such as fuses or the like. Also the inductance element I may be of comparatively small size, since it decreases the voltage between the line voltage of 110 to approximately 60-65 volts across the electrodes of the lamp.

Referring now to Fig. 2, the circuit differs from that of Fig. 1 in that the various elements thereof are not necessarily selected to make the circuit at or near resonance for the frequency of the supply source. In addition, what has been termed a thermal silicon relay I5, or the like, has been substituted for the resistance device Il oi Fig. 1.

However, this relay is very similar to the resistance element I0 in that it has a negative temperature coefficient and differs from the resistance element I0 solely in the provision oi' a coil I6 sur,`

rounding the device, which is heated by the now of current through the device. One end of this coil I0 is connected to one end of the tubular portion of the device Il and one side of the capacitor I2, which latter in this particular modincation may be of much smaller size of approximately 2 microfarads.

IIhe coil Il consists of a metal responsive to temperature changes, and its opposite 'end is provided with a small contact I'I which, when the device is cold, establishes a connection with a stationary contactor Il, the latter of which is connected by means of a conductor I9 to the opposite side oi the capacitor I2.

In this circuit the capacitor I2 is used to produce a high voltage for starting the lamp 5 and is of such size as to impress a high enough starting voltage across the electrodes with the filaments hot to initiate a discharge, but which does not draw enough current to heat the filaments. Consequently, the thermal relay Ii is utilized to connect the electrodes in series and to short-circuit the capacitor I2 until the electrodes have reached an electron-emitting temperature, at which time the relay opens, thus connecting the capacitor again in the circuit for impressing a sufficiently high starting voltage across the electrodes.

In the normal or cold position of the thermal relay I5, the contacts I'I and Il are closed. Upon closure oi the switch (not shown), energy will be supplied from the source 8 which will flow through the inductance element 8, electrodes i and I and thermal relay Il. This flow of current heats the electrodes 6 and I to an electron-emitting temperature in the same manner described relative to Fig. 1 and at the same time causes a gradual increase in the temperature oi the thermal relay I5.

As the temperature of this latter device gradually increases, it heats the coil I0, causing the contacts I'I and I8 to open due to the thermal characteristics of the material of which the coil is composed, thus connecting the capacitor I2 in series with the electrodes in the same manner as previously described with reference to Fig. l.

Frequently the transient voltage flowing through the inductance S is suiiicient to give a voltage kick higher than the line voltage and Vinitiate an arc, but in order to assure a sufiicently high enough starting voltage, .the capacitor I2 is nevertheless included in the circuit. This allows the voltage to build up across the capacitor to the value required to initiatey a discharge between the electrodes 6 and l. Again, as in Fig. 1, upon the initiation of a discharge, the current through the device I5 is inappreciable, since current now is across the path of leest resistance, namely, the discharge.

The thermal' relay I5 will accordingly decrease In temperature and again close the contacts I`I and Il. However, as the resistance oi' the device I5 is very high when cold, practically no current will flow therethrough, since the voltage across the lamp has decreased to approximately 60-65 volts.

By reference to Fig. 3, one form of thermal relay is shown wherein the core may consist of a glass tube illled with silicon crystals, or a solid rod oi' carborundum or zinc oxide as hereinbeiore mentioned. This core is surrounded by a helical metallic winding or coil having a suitable thermal expansion so that when cold, its free end tiexes laterally to make and break contact with the stationary terminal or contact Il, as shown more clearly by the full and dotted lines in Fig. 4.

In Fig. 5 a slightly different modification of the thermal relay forming a part of the present invention is shown. In this embodiment, the stationary contact Il is of angular connguration and disposed adjacent one side of the core I5. A metallic strip responsive to temperature changes is supported in a saddle 22 so that when no current is flowing through the core I6, and hence the relay is cold, the strip 20 sags in the center so that a laterally extending pin 28 secured thereto, and corresponding to the contact l1, engages the stationary angular contact IB.

When current tlows through the core i5 and the temperature thereof increases, the strip 20 expands and rises to the position shown by the dotted lines in Fig. 5, thus opening the contacts i8 and 2! with the result as previously described with reference to Fig. 2.

It thus becomes obvious to those skilled in the art that a starting circuit for a gaseous discharge device is herein provided wherein the device may be operated from the customary domestic source of supply. Moreover, a resistance device is employed having a negative temperature coefilcient which, when cold, has a high resistance to the flow of current. This device, being connected in series with a capacitor and the electrodes of the lampl allows the gradual iiow of current therethrough until the electrodes are raised to an electron-emitting temperature.

Shortly after the electrodes reach an electronemitting temperature, the resistance device enables an increased ow of current so that a starting voltage may be built up in the capacitor, which then delivers a suiiciently high starting voltage to initiate a discharge between the electrodes. Upon the initiation of the discharge, the resistance device cools oi, automatically increasing its resistance to a high enough value as to substantially preclude the iiow of current therethrough, thus operating to interrupt the ow of heating current through the electrodes, enabling the latter to be sustained at an electron-emitting temperature solely by the heat generated by the discharge.

In addition, a thermal relay has been herein shown and described, which relay has a negative temperature coeil'lcient. This device may be incorporated in the starting circuit for a gaseous discharge device and operates t0 connect a capacitor to the circuit for the purpose oi' supplying a voltage in excess of the normal line voltage for initiating a discharge, after which the capacitor is again shunted from the circuit.

In botlrv the modications herein shown and described, the device utilized for interrupting the flow of heating current through the electrodes is such as to consume no power during operation of the device.

Although several embodiments of the present invention have been shown and described, it is to be understood that other embodiments thereof may be made without departing from the spiri and scope of the appended claims.

What is claimed:

1. The combination of an electric discharge device comprising a container having a gaseous atmosphere therein, electrodes sealed in said container and each provided with a pair of terminals, a source of electrical energy of the usual domestic potential connected to one terminal of each alectrode, and means having a negative temperature coefilcient of resistance interposed between the remaining electrode terminals for connecting said electrodes in series to said source to heat said electrodes, to an electron-emitting temperature and operable to reduce the flow of heating current through said electrodes upon initiation of a discharge between said electrodes.

2. The combination of an electric discharge device comprising a container having a gaseous atmosphere therein, electrodes sealed in said container and each provided with a pair of terminals, a source of electrical energy of the usual domestic potential connected to 'one terminal of each electrode, a self-inductance element interposed between said source and the terminal of one of said electrodes, and means interposed between the remaining electrode terminals for connecting said electrodes in series to said source to heat said electrodes to an electron-emitting temperature, said means including'an element having a negative temperature coeflicient of resistance and a high resistance when cold which gradually decreases as said element becomes heated simultaneously with heating of said electrodes and operable to reduce the flow of heating current through said electrodes upon the initiation of a discharge between said electrodes.

3. The combination of an electric discharge device comprising a container having a gaseous atmosphere therein, electrodes sealed in said container and each provided with a pair of terminals, a source of electrical energy oi' the usual domestic potential connected to one terminal of each electrode, a self-inductance element interposed between said source and the terminal of one of said electrodes, and means interposed be-v tween the remaining electrode terminals for connecting said electrodes in series to said source to heat said electrodes to an electron-emitting temperaturel said means including an energy accumulating device for storing and delivering a starting voltage sufficient to initiate a discharge between said electrodes, and an element having a negative temperature coeil'icient of resistance and a high resistance when cold which gradually decreases as said device becomes heated simultaneously with heating of said electrodes and operable to reduce the flow of heating current through said electrodes upon initiation of the discharge.

4. The combination of an electric discharge device comprising a container having a gaseous atmosphere therein, electrodes sealed in said container and each provided with a pair of terminals, a source of electrical energy of the usual domestic potential connected to one terminal of each electrode, a, self-inductance element interposed between said source and the terminal of one of said electrodes, and means connecting said electrodes in series to said source of electrical energy to heat said electrodes to an electronemitting temperature and for reducing the flow of heating current through said electrodes upon the initiation of a, discharge between said electrodes, said means being so proportioned relative to said self-inductance element that they are in resonance for the fundamental frequency of the source.

5. A circuit for starting and operating an electric discharge device having electrodes therein to be heated to an electron-emitting temperature prior to the initiation of a discharge and each provided with a pair of terminals comprising a source of electrical energy of the usual domestic potential connected to one terminal of each of said electrodes, and an energy storage device and an element having a negative temperature coeillcient of resistance connected to the remaining terminals of said electrodes to connect the latter in series to said source of heating said electrodes to an electron-emitting temperature, and for supplying a voltage to said electrodes sumciently high to initiate a discharge. and said element having a negative temperature coemcient of resistance being operable to reduce the flow of heating current through the series connected electrodes upon the initiation of the discharge.

6. A circuit for starting and operating an electric discharge device having electrodes therein to be heated to an electron-emitting temperature prior to initiation oi' a discharge and each pro vided with a pair of terminals comprising a source of electrical energy of the usual domestic potential connected to one terminal of each oi said electrodes, and an energy storage device and an element having a negative temperature coemcient of resistance connected in series with each other and with the remaining terminals oi said electrodes. said energy storage device being operable to supply a starting voltage to said electrodes sufilcient to initiate adischarge alter said electrodes have attained an electron-emitting temperature, and said element having a negative temperature coemcient oi resistance being operable to gradually decrease in resistance as it becomes heated by said source simultaneously with the heating of said electrodes and operable to increase in resistance and reduce the flow of heating current through said electrodes following initiation of the discharge.

7. A circuit for starting and operating an electric discharge device having electrodes therein to be heated to an electron-emitting temperature prior to initiation of a discharge and each provided vvith a pair oi' terminals comprising a source of electrical energy of the usual domestic potential connected to one terminal of each of said electrodes, means adapted to be connected to the electrodes of said discharge device for supplying a starting voltage suillcient to initiate a discharge, and a thermal relay having a negative temperature coeiilcient of resistance interposed between the remaining terminal ci said electrodes for connecting said electrodes in series to said source to heat said electrodes to an electron-emitting temperature, and said thermal relay being operable to open and close a low resistance path in parallel with said means and to reduce the flow of heating current through said electrodes upon the initiation of a discharge therebetween.

8. A circuit for starting and operating an electric discharge device having electrodes therein to be heated to an electron-emitting temperature prior to initiation of a discharge and each provided with a pair of terminals comprising a source of electrical energy of the usual domestic potential connected to one terminal oi each o! said ,electrodes. an energy accumulating device adapted to be connected to the electrode of said discharge device for accumulating a starting voltage and delivering the same to said electrodesl to initiate a discharge therebetween, and a thermal relay having a negative temperature ooeiilcient oi resistance interposed between the remaining terminal oi said electrodes for connecting said electrodes in series to said source to heat said electrodes to an electron-emitting temperature, said thermal relay being provided with contact terminals operable to complete a parallel circuit including said energy accumulating device upon the relay becoming heated simultaneously with the heating oi.' said electrodes. and operable to reduce the now of heating current through said electrodes upon the initiation ot a discharge therebetween.

9. 'Ihe combination o! an electric discharge lamp having a pair of electrodes one of which is of the nlamentary type, an inductance element in series with said lamp, an impedance device connecting one end oi' the tllamentary electrode to the other electrode, and a thermo-expansive element in position to be distorted by the heat developed in said impedance device when the latter passes current to cause a variation in the current supplied to said illamentary electrode.

10. The combination of an electric discharge lamp having a pair of electrodes one of which is of the illamentary type, an inductance element in series with said lamp, an impedance device having a negative temperature coemcient of resistance connecting one end o! the illamentary electrode to the other electrode, and a thermo-expansive element in position to be distorted by the heat developed in said impedance device when the latter current to cause a variation in the current supplied to said illamentary electrode and initiation of a discharge between said electrodes.

l1. The combination of an electric discharge lamp having a pair of electrodes one oi which is of the illamentary type, an inductance element in series with said lamp, an impedance device connecting one end of the filamentary electrode to the other electrode and having an impedance large compared with that of said inductance element. and a bimetallic element in position to be distorted by the heat developed in said impedance device when the latter current to cause a variation in the current supplied to said filamentary electrode and initiation of a discharge between said electrodes.

DANIEL S. GUSTIN. ROBERT FRED HAYS, Jn. 

